Fix remaining dependabot alerts (#1388)

- Updated @microsoft/generator-powerpages to 1.39.3
- Added npm overrides to force vulnerable packages to safe versions:
  - tmp: ^0.2.4 (was <= 0.2.3)
  - @octokit/request: ^8.4.1 (was <= 8.4.0)
  - @octokit/plugin-paginate-rest: ^9.2.2 (was <= 9.2.1)
  - @octokit/request-error: ^5.1.1 (was <= 5.1.0)
- Fixes dependabot alerts #87, #69, #68, #67

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Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Author: priyanshu92